Studies on early events which lead to the induction of SOS functions will be continued by using a newly developed permeable read-through transcription-translation system. Phage repressor molecules are inactivated in this system either after UV irradiation or following addition of four deoxyribonucleoside triphosphates and ATP. Efforts will be made to isolate an effector molecule(s) which signals SOS induction. Studies on E. coli transformation will be continued with a specialized transformation system in which a marker on plasmids is transformed by a fragment of DNA.